Scoop the mango pieces in a bowl.
Heat oil in a sauce pan and chopped onions, ginger to it.
Once, onions are pink, add chopped mangoes to the pan.Mix well
Add vinegar, sugar, garam masala and cardamom powder to it,cook on low flame, allow it to come to boil
Now add raisins to it and mix well.
Let it cook until it thickens to a chutney like consistency.
Store in a clean glass jar in a refrigerator for next few weeks, always use a clean and dry spoon to serve